I've been around Hummingbird for 1 1/2 year, sort of. As mentioned in my introduction thread I did an account wipe/switch lately to sort out stuff and have a restart, since things changed here.
I started getting more active in Forum/Feed activity lately, following some users, and I must say, besides a few group posts and some discussions in the feed, there is not much activity. But, I personally don't consider the Feed as main source of Interactions, as it really isn't suited for this.
Sure, active users and general activity might be on a lowpass right now, but Hummingbird is a fresh service. 2 years old and there are ups and downs, I just know this myself. As some people already read, I'm one of the project leaders and main developers behind the Q/A platform Retrospring, and, currently having around 4272 users after 8 months of public testing, as we still add features over time. There were days we got no users and almost no activity and there were other days, were people visited the site so often, that our server almost broke down. Since Hummingbird is also pretty young it's about the current community shaping the site, just complaining "nothing to do here, I quit" won't make it better for anyone else registering and using the site later.
Something that would help people to find interesting users would be the Compare-feature, which is marked off "Coming Soon!" in the forum view of a profile, to help finding people with a similar taste in anime, giving a list of recommended people to follow.
I also wouldn't mind helping out with the code, at least as far as I can help with it, after getting into the codebase and knowing where to do what.
The big problem I see with Hummingbird is the seperation of the main site and the forums. Sure, content is shared besides them, like the profiles etc.pp., but that's pretty much about it. Getting forum notifications on the main site and site notifications on the forum, having them all at one place would probably be handier than not knowing what's happening on the other end of HB. But of course, I understand that, the two possibilities, either clutching Discourse and HB close together, or coding a own small forum solution, would require a lot of work.
Also, about Skype. I'm not really sure if a Instant Messenger manages to kill off a community with having groups of people from aforementioned one in it. Skype just extends the ways of interacting with each other, real-time messages and stuff, but besides that, also...managing bigger groups of people...in short, it generally sucks.
I actually had the idea of arranging some sort of "anime watch sessions" on my Mumble (VoIP) server, to get some parts of the community closer together, if people would be interested in it.
As of now, what I can say, as some sort of "summary": The current users have to bring the activity they want, being creative, also probably telling friends about the site, helping the community grow, there are a lot of ways you can help that the site can get more activity overall.